1. Field of the Invention
The invention relates to a vehicle steering system.
2. Discussion of Background
A vehicle steering system includes a steered shaft that moves in its axial direction in response to an operation of a steering wheel, and a tubular housing that covers the steered shaft. Wheels are coupled to respective end portions of the steered shaft via joints, tie rods and the like. The end portions of the steered shaft, the joints, the tie rods and the like project from the housing, and are covered with bellows.
Japanese Patent Application Publication No. 2008-137473 (JP 2008-137473 A) describes a rack for a steering system. According to JP 2008-137473 A, rack ends, which are fixed to respective end portions of a steered shaft having the rack and which are larger in diameter than the steered shaft, come into contact with corresponding stoppers arranged in a housing, thereby restricting the amount of movement of the steered shaft.
In a material-handling vehicle such as a fork lift, a tie rod angle (an angle formed by a steered shaft and each tie rod in a planar view) is larger than that in an ordinary vehicle. Therefore, it is not possible to provide bellows because they would fail to expand and contract in accordance with the movement of the tie rod. This creates the possibility that foreign matter, for example, gravels will be caught between the rack ends and the stoppers. In order to avoid this possibility, stepped portions may be formed in a steered shaft at sections that are located in a housing, and the stepped portions may be brought into contact with corresponding stoppers of the housing to restrict the amount of movement of the steered shaft. However, if a bending load is applied to the steered shaft that has the stepped portions, stress concentration may occur at the stepped portions and large stress may be generated at the stepped portions.